X-ray tube anode seal



7, I N. H. STEWART 2,381,625

X-RAY TUBE ILNODE SEAL Original Filed Jan. 27; 1942 Mmhwz ATTORNEY Patented Aug. 7, 1945 Nelson H. Stewart, Fairm Westinghouse Electric burgh, Pa., a corporati Original application Jan 428,358, now Patent tember 19, 1944. October 15, 1943,

ont, W. Va., assignor to Corporation, East Pittson of Pennsylvania uary 27, 1942, Serial No.

No. 2,358,668, dated Sep- Divided and this application Serial No. 506,324

6 Claims. (oi. 29 25.14)

This invention relates to the fabrication of an anode for an X-ray tube, especially to such anodes which include a copper rod supporting a press element and consisting substantially of nickel, kobalt and iron or like metal capable of being readily united to the glass of the press, and the invention relates more particularly to the joint between the copper rod and the Kovar and the method of forming such union. The present application constitutes a division of my copending application Serial No. 428,358, filed January 27, 1942, now'Patent No. 2,358,668, issued September 19, 1944; i I

In the usual type of copper anode using a Kovar seal, the Kovar'is soldered to the anode after the anode has been machined. In addition to the fact that some losses are eX- perienced due to poor soldering, the latter constitutes an extra operation which can be avoided, thus cheapening the manufacturing costs of an anode, according to the results attending my researches in this field,

Accordingly, an object of this invention is to avoid the disadvantages and inconveniences incidental to the use of a soldered joint between the Kovar element and its copper support by elimi nating the use of solder in that connection.

Another object is to cut down the number of operations in forming the aforesaid joint by uniting the Kovar to the copperat the same time that the copper is cast.

A further object is to provide means to produce the cast Kovar-copper" joint in such a manner that the cast product can be readily machined to a shape which facilitates the step'of sealin the Kovar element into the glasspress by which the anode is eventually integrated with the X-ray tube.

Still another object is' to provide apparatus which can be used over and over for the fabrication, seriatim, in quantity production," of anodes made accordingto the present invention, each of the anodes constituting'a complete anodeunit as an intermediate product ready for incorporation in its X-ray tube by the use of substantially conventional machinery. l v

A cognate object isto provide a complete anode unit of relatively few, sturdy parts, free from the presence-of residual corrosive material used in every soldered joint, in place of which 'isutilized, according to my invention, a thoroughly reliable cast union between the copper supporting rod and the Kovar seal, the novel anodes thus produced being capable of being stored, transported and supplied in desired quantities as such.

of the alloy known .as Kovar Other objects and features of the invention will be made apparent to those skilled in the art as progress is made with the description of the embodiment of the invention elected for illustration in the accompanying drawing wherein:

Fig. 1 is a View in side elevation, partly in section, of an anode for an X-ray tube, in the construction of which the present invention has been embodied;

Fig. 2 is a view in vertical section, showing an assembly of the component elements for making the anode of Fig. 1 and including the crucible in which said assembly is placed ready for subjection to the heat of a suitable furnace;

Fig. 3 is a view in sectional elevation illustrating the assembly of Fig. 2 disposed within the furnace, and showing the parts in their position after application of the necessary heat;

Fig. 4 shows the anode removed from the furnace and crucible and partly machined.

Referring now to the drawing in detail, the

part designated by the reference character II is a'copperrod which in the instance shown is to constitute'the body of the anode in the completed produ ct, the latter being shown in Fig. 1, while in Fig. 2 the copper element is indicated as a slugat l 0, being as yet unshaped.

Acrucible I2 is shown into which th copper slug Ill is placed, after first disposing at the bottom of the crucible a block I3 of carbon on which lies; the anode target 14, in the inclined position which it is :to occupy in the completed anode, as shown in Fig. 1. T On top of the copper slug 10 is then placed a carbon bushing 15, which serves to hold in place theKovar element IS, the latter shown as taking the form of a cylinder or thimble having a lip ll. In order to cause this element 1 6 to sink into the copper when the latter is in a molten state, as indicated at C in Fig. 3, it is weighted in any suitable manner either by placing a weight on top of the thimbl I6 or by disposing such weight 18 made of a metal having a higher melting point than copper inside the thimble either on a shoulder provided for that purpose or on the closed end of the thimble as shown in Figs. 2 and 3. This weight I8 is such as to overcome the buoyancy of the Kovar thimble and cause it tosink the desired distance but as a further limit on the depth to which the thimble sinks in the molten copper, the lip I1 is provided although this is not necessary if the weight 18 is carefully selected.

1 In operation, when the assembly of Fig. 2 has been placed in the furnace I9 and a suitable degree of heat applied, the copper slug l melts and flows down and around the target M in known fashion, and the weight l8 draws the thimble 16 down into the molten copper and. at the same tim draws the lip ll of the thimble against the top of the carbon bushing until stopped by engagement of the bottom of the bushing with the upper surface of the molten copper, at which time all of the parts occupy the position shown in Fig. 3.

The crucible l2 and its associated parts may be removed from the furnace I9, and after allowing the copper to solidify, the partly completed anode will be removed from the crucible, when it presents the appearance shown in Fig. 4, according to which it is clear that I have formed a sturdy cast joint between the copper rod II and the Kovar seal H5 at the same operation as that of casting the copper, thus eliminating the previously required step of soldering the seal-forming thimble to the copper rod.

After turning off the lip ll of th thimble I6 if such is employed, the carbon bushing l5 may be slid off the Kovar thimble and can be used as many times as its condition permits, together with the carbon block i3 and the crucible l2, these being permanent parts of my novel apparatus. The anode is now ready to be machined in known fashion, the top edge of the thimble I6 being preferably tapered, as indicated at 2| in Fig. l, where it enters the glass press 22 to form the Kovar seal in known manner. The anode illustrated in Fig. 1 is a complete article of manufacture, ready for its intended use in an X-ray tube, and is a unit capable of being stored with other like units, transported as such, and installed at will. 1

I claim:

1. In the method of fabricating anodes for X-ray tubes, each anode having a copper supporting rod, 9. glass press and a seal made of a metal capable of uniting readily with the glass of said press, said method comprising inserting a copper slug adapted to form said copper rod in an upright crucible, superimposing upon said slug in the crucible a metallic thimble seal element which readily unites with glass surrounded by a spacing bushing also resting upon said slug, weighting said thimble to cause penetration of its lower end into said copper when the latter is molten, heating said crucible and its contents until said penetration takes place to a predetermined extent to form a cast joint between the copper and the thimble seal element, cooling said crucible and its contents, removing the copper rod and bushing from the crucible, and freeing said bushing from the thimble.

2. The method of fabricating anodes for X- ray tubes, each anode having a copper supporting rod, a glass press and a seal "made of a metallic alloy consisting substantially of nickel, kobalt and iron capable of uniting readily with the glass of said press, said method comprising inserting a copper slug adapted to for-m said cop'- per rod in an upright crucible, superimpos'mg upon said slug in the crucible a thimble of metallic alloy surrounded by a carbon spacing bushing also resting upon said slug, weighting said thimble to cause penetration of its lower end into said copper when the latter is molten, heating said crucible and its contents until said penetration takes place to a predetermined extent to form a cast joint between the copper rod and the metallic thimble, cooling said crucible contents, removing the copper rod and bushing from the crucible, freeing said bushing and removing the same from the thimble, uniting the free end of said metallic thimble with the glass press, and machining said complete anode.

3. Apparatus for fabricating anodes for X- ray tubes, comprising a crucible adapted to receive and melt when heated a slug of copper to the shape of a supporting rod as an element in the complete anode, a spacing bushing of carbon resting upon said slug in the crucible until the copper is melted to hold centrally of the crucible a seal thimble of metal capable of ready attachment to the glass press of the anode, and a weighting means adapted to force the lower "end of said thimble into the molten copper to form a cast joint between'the copper rod and the metal seal thimble.

4. Apparatus for fabricating anodes for X- ray tubes comprising a crucible adapted to receive and melt when heated a slug of copper to th shape of a supporting rod as an element in the complete anode, a carbon block for supporting the refractory metal target, a spacing bushing of carbon resting upon said slug in the crucible until the copper is melted to hold centrally of the crucible a metal seal element capable of ready attachment to the glass press of the anode, and a weighting means adapted to force the lower end of said metal seal element into the molten copper to form'a, cast joint between the copper rod and the metal seal element; said crucible, carbon block for said target, the carbon bushing for the metal seal element, and the weighting means, all being formed removably from each other and usable in .assembly an indefinite number of times in the fabrication of a series of identical anodes.

5. Apparatus for fabricating anodes for X- ray tubes comprising a crucible adapted to receive and melt when heated a slug of copper to the shape of a supporting rod as an element in the complete anode, a spacing bushing of carbon resting upon said slug in the crucible until the copper is melted to hold centrally of the crucible a metallic seal thimble consisting substantially of nickel, kobalt and iron capable of ready attachment to the glass press of the anode, and a weighting means adapted to force the lower end of said thimble into the molten copper to form a cast joint between the copper rod and the metallic seal thimble.

6. Apparatus for fabricating anodes for X ray tubes comprising a crucible adapted to receive and melt when heated a slug of copper to the shape of a supporting rod as an element in the complete anode, a carbon block for supporting the refractory metal target, a spacing bushing of carbon resting upon said slug in the crucible until the copper is melted to hold centrally of the crucible a metallic seal thimble consisting substantially of nickel, kobalt and iron capable of ready attachment to the glass press of the anode, and weighting means adapted to force the lower end of said thimble into the molten copper to form a cast joint between the copper rod and the metallic seal thimble; said crucible, carbon block for said target, the carbon bushing for the thimble, and the weighting means, all being formed removably from each other and usable in assembly an indefinite number of times in the fabrication of a series of identical anodes.

NELSON H. STEWART. 

